Impaired autophagy increases susceptibility to endotoxin-induced chronic pancreatitis

Abstract

Chronic pancreatitis (CP) is associated with elevated plasma levels of bacterial lipopolysaccharide (LPS) and we have demonstrated reduced acinar cell autophagy in human CP tissue. Therefore, we investigated the role of autophagy in experimental endotoxin-induced pancreatic injury and aimed to identify LPS in human CP tissue. Pancreatic Atg7-deficient mice were injected with a single sub-lethal dose of LPS. Expression of autophagy, apoptosis, necroptosis, and inflammatory markers was determined 3 and 24 h later utilizing immunoblotting and immunofluorescence. The presence of LPS in pancreatic tissue from mice and from patients and healthy controls was determined using immunohistochemistry, immunoblots, and chromogenic assay. Mice lacking pancreatic autophagy exhibited local signs of inflammation and were particularly sensitive to the toxic effect of LPS injection as compared to control mice. In response to LPS, Atg7Δpan mice exhibited enhanced vacuolization of pancreatic acinar cells, increase in TLR4 expression coupled to enhanced expression of NF-κΒ, JNK, and pro-inflammatory cytokines by acinar cells and enhanced infiltration by myeloid cells (but not Atg7F/F controls). Cell death was enhanced in Atg7Δpan pancreata, but only necroptosis and trypsin activation was further amplified following LPS injection along with elevated pancreatic LPS. The presence of LPS was identified in the pancreata from all 14 CP patients examined but was absent in the pancreata from all 10 normal controls. Altogether, these results support a potential role for metabolic endotoxemia in the pathogenesis of CP. Moreover, the evidence also supports the notion that autophagy plays a major cytoprotective and anti-inflammatory role in the pancreas, and blunting metabolic endotoxemia-induced CP.

Emerging roles of ATG7 in human health and disease

“…In the pancreas, loss of Atg7 causes premature death due to declining exocrine and endocrine function (Zhou et al , 2017 ). Atg7 deletion also appears to increase susceptibility to endotoxin‐induced chronic pancreatitis (Xia et al , 2020 ). Atg7 maintains islet architecture, glucose tolerance and serum insulin levels and is important for islet homeostasis and compensatory pancreatic responses to high‐fat diet (Ebato et al , 2008 ; Jung et al , 2008 ; Himuro et al , 2019 ).…”

ATG7-enhanced impaired autophagy exacerbates acute pancreatitis by promoting regulated necrosis via the miR-30b-5p/CAMKII pathway

“…ATG7 plays a significant role in the initiation of autophagosome formation. We should not convert the former impaired autophagy derived from the overactivation of upstream formative pathway in response to AP modeling to the latter one derived from insufficient activity of autophagy, given that the basal physiological activity of autophagy in response to AP modeling is indispensable to provide some protection [ 42 , 43 ]. The ideal range of activated autophagy in response to AP modeling, which may be suggested by some well-quantified parameters, is worthy of elucidation in future studies.…”

Understanding Necroptosis in Pancreatic Diseases

“…With the increase in CP incidence and prevalence, there is no effective treatment. The expression levels of LPS in the pancreatic tissues of mice, healthy patients, and the control group were determined by immunohistochemistry (IHC) and Western blotting (WB), and necroptosis and trypsin activation were amplified in mice after LPS injection, which supported the potential role of LPS in the pathogenesis of CP [ 109 ]. LPS can also induce the necroptosis pathway and exacerbate the inflammatory response.…”